Method of and means for heat-treating refractory materials at high temperatures



June 10, 1969 w, BRZOZOWSK] ET AL 3,449,505

METHOD OF AND MEANS FOR HEAT-TREATING REFRACTORY MATERIALS AT HIGH TEMPERATURES Sheet of 2 Filed May 19, 1966 W. Brzozowski i M. Miko t t I J. Niewlladomski INVENTORS.

011 53 2 1A 6 Attorney June.10, 1969 w, BRZOZOWSK] ET AL 3,449,505

METHOD OF AND MEANS FOR HEAT-TREATING REFRACTORY MATERIALS AT HIGH TEMPERATURES Filed May 19, 1966 Sheet 2 of 2 Wojciech Brzozowski Michal Mikos' Janusz Niewiadomski INVENTORS.

A. [to Lie y United States Patent US. Cl. 13--1 9 Claims ABSTRACT OF THE DISCLOSURE A material to be subjected to high treatment temperatures is placed in a crucible inside a furnace chamber and exposed to radiant heat from a vertical plasma flux rotating about the crucible axis.

The invention relates to a method of obtaining high temperatures in plasma furnaces and to a device for a1 plication of this method. In further description this device is simply named plasma furnace. It is based on the principle of a laminar plasma flux or of a laminar plasma column of an electric are moving over a generating surface of a cylinder.

Application of a plasma flame of a temperature range 4,00010,000 K. opens quite new possibilities in the field of researches on refractory materials at high melting temperatures.

The plasma furnace shown by way of example is a laboratory-type unit of a comparatively small capacity at maximum temperature, having a volume of about 1000-2000 cc. Nevertheless, according to the described principle also much greater units for industrial use may be built.

So far only the direct plasma flame activity has 'been utilized for melting the materials at a temperature exceeding 3,000 C. Small samples of heat-resisting materials have been placed in the plasma flux in order to melt them, or to effect in them some desired chemical reactions. The heating of materials was usually rendered more difficult by dynamic reaction of the flux (high kinetic energy of the plasma flux, blowing-out of the melted material etc.)

In some processes of the nuclear technology the described method has found its utilization, e.g., for spheroidization of uranium oxides and carbides, for fusion of uranium and plutonium carbides, etc.

The plasma furnace according to our present invention, in which temperatures considerably higher than 3,000 C. may be obtained, is based upon a different solution, two embodiments of which are described below with reference to the accompanying drawing in which:

FIG. 1 is an elevational view of a plasma furnace representing a first embodiment;

FIG. 2 is a top view of the furnace of FIG. 1; and

FIG. 3 is a view similar to FIG. 1, showing a second embodiment.

In FIGS. 1 and 2 there is shown a first embodiment of a high-temperature plasma furnace. A source of radiant heat for a crucible 7 is represented by a laminar plasma flux 2 emitted into a treatment chamber 13 from a plasmatron nozzle 1. In order to obtain a temperature field as nearly uniform as possible, travels along a circular orbit of radius R centered on the axis of the crucible 7. which is shown as an upwardly open receptacle. The laminar flux of plasma 2 moves then over the generating surface of a cylinder of radius R and heats up the crucible uni- 3,449,505 Patented June 10, 1969 formly from all sides. It will be noted that the elongate plasma flux 2 is parrallel to the axis 12 of crucible 7 and chamber 13.

The plasmatron in its circular motion is driven by means of a mechanism shown in FIGS. 1 and 2: a motor 3 drives the furnace cover 4 in which the plasma generator is eccentrically positioned to perform the aforedescribed revolution of radius R. The length of the radius R may be adjusted by means of the eccentric 5. A guide 0 bar 10 prevents the plasmatron 1 from rotating around its own axis, except over a minor oscillatory range of up to 40 as indicated by the double-heated arrow in FIG. 2.

In the above-described embodiment of the plasma furnace according to our invention, the temperature in the vicinity of the crucible 7 may be varied over a wide range, during the process of heating its contents, by the following measures: (a) by controlling the power applied to the plasmatron 1; (b) by changing the height H of the crucible 7; (c) by changing the radius R; and (d) by changing the speed of the plasma flux 2.

In FIG. 3 there is shown a second embodiment of the plasma furnace in which the heating element is the laminar plasma column of an electric are 11 showing between plasmatron 1 and a ring-shaped anode 8 concentric with axis 12.

In the embodiment of FIG. 3 the plasmatron also rotates in a circular orbit of radius R around the crucible center (i.e. the vertical axis 12 of the furnace chamber 13, and the revolving arc column 11 generating a cylinder of radius R assures an uniform temperature distribution in the vincinity of the crucible 7. The plasma furnace according to the second embodiment aflords still higher temperatures around the crucible 7 than the embodiment of FIGS. 1 and 2.

Controlling of the temperature in the second embodiment of the invention is effected by (a) controlling the power applied to the plasmatron 1; (b) changing the radius R of the orbital path of the arcuate plasma 11. Radius R may be varied discontinuouly in steps, just after plasmatron 11 has been switched off; and (c) varying the speed of the plasmatron 1 along its orbit of radius R, e.g. between 10 and revolutions per minute.

What we claim is:

1. A method of heat-treating a material at high temperatures, comprising the steps of placing said material at a predetermined location in a chamber generating a plasma flux in said chamber substantially parallel to an axis in line with said location and at a distance R from said axis, and revolving said plasma flux about said axis in an orbit of radius R while subjecting said material to radiant heat from said flux.

2. A method as defined in claim 1 wherein said flux is substantially vertical.

3. A method as defined in claim 2 wherein said flux is downwardly directed.

4. A method as defined in claim 1 wherein said plasma flux is limitedly oscillated about its own axis while revolving in said orbit.

5. A device for heat-treating a material at high temperatures, comprising a treatment chamber, a receptacle in said chamber for material to be treated, a plasma generator adapted to produce an elongate plasma flux in said chamber, rotatable supporting means for said generator centered on an axis in line with said receptable, said generator being mounted at a location remote from said axis, and drive means for rotating said supporting means about said axis whereby said plasma flux revolves around said receptacle.

6. A device as defined in claim 5 wherein said genertor is adjustably disposed on said supporting means for varying the distance of said. location from said axis.

7. A device as defined in claim 5 wherein said re ceptacle is an upwardly open crucible, said axis being ator is disposed at the top of said chamber for directing 5 said flux downwardly into same.

9. A device as defined in claim 5 wherein said generator includes an annular anode in said chamber center on said axis.

4 References Cited UNITED STATES PATENTS 2,922,869 1/1960 Giannini et a1. 3,147,329 9/1964 Gage 139 BERNARD A. GILHEANY, Primary Examiner. R. N. ENVALL, JR., Assistant Examiner.

US. Cl. X.R. 219-121 

